Foil-baked Whole Fresh Salmon with Green Herb Mayonnaise

The way I cook a salmon is extremely slowly, wrapped in foil in the oven. I cannot recommend this method highly enough. With skin and bones, head and tail intact there is not only a captured concentration of flavours, but also a guaranteed succulent moistness that no other cooking method can produce. It's also probably the easiest thing to cook for a large number of people with absolutely no hassle. The best accompaniment is a sweet, very green mayonnaise flavoured with summer herbs, which I think is best made the day before, if possible, to allow the flavours to develop. This recipe is for a 4 lb (1.8 kg) salmon. For other weights of salmon, the cooking times are: for 2 lb (900 g) 1½ hours; for 3 lb (1.3 kg) 2 hours; for 5 lb (2.25 kg) 3 hours. Unfortunately, the gas equivalent of 250°F (130°C), which used to be gas mark ½, no longer exists. So, if you use a modern gas cooker that begins at gas mark 1, give the fish 25 minutes less cooking time.

Serves 8

This recipe is taken from How to Cook Book Three and The Delia Collection: Fish.

Ingredients

4 lb (1.8 kg) fresh whole salmon

2 oz (50 g) butter, plus extra for buttering the kitchen foil

1 small onion, peeled and thinly sliced

3 bay leaves

4 sprigs tarragon

salt and freshly milled black pepper

For the green herb mayonnaise:

2 eggs

2 level teaspoons mustard powder

1 fat clove garlic, peeled

½ pint (275 ml) groundnut oil

2 dessertspoons white wine vinegar

3 oz (75 g) fresh spinach leaves

1½ oz (40 g) watercress leaves

1½ oz (40 g) flat-leaf parsley leaves

2 tablespoons fresh tarragon, chopped

1 tablespoon snipped fresh chives

1 tablespoon lemon juice (or more to taste)

salt and freshly milled black pepper

Equipment

Method

First make the mayonnaise. Break the whole eggs straight into the goblet of a blender or food processor, sprinkle in the mustard powder and add the garlic clove and 1 level teaspoon salt. Then measure the oil into a jug, then switch the machine on. To blend everything thoroughly, pour the oil in a thin, very steady trickle with the motor running. You must be very careful here – too much oil in too soon means the sauce will curdle. When all the oil is in, add the white wine vinegar and blend. Then switch off and season to taste with salt and freshly milled black pepper.

Now rinse the spinach, watercress and parsley under cold water and put these into a medium saucepan. With the heat turned to medium, stir the leaves around until everything has just wilted, then tip them into a colander and rinse under cold water to keep the colour. Now squeeze out the excess moisture very carefully, thoroughly pressing and squeezing with a wooden spoon. Then transfer the cooked leaves to the mayonnaise in the blender with the chopped tarragon and chives and whiz until smooth and green. There will be some fine specks but that's okay. Now do a bit of tasting and season with lemon juice, salt and pepper.

When you are ready to cook the salmon, preheat the oven to 250°F (130°C) – see introduction for important information about the gas mark.

Start by wiping the fish with some damp kitchen paper, then place it in the centre of a large double sheet of foil, generously buttered. Put half the butter, the onion slices, bay leaves and tarragon sprigs into the centre cavity of the fish, along with a seasoning of pepper and salt. The rest of the butter should be smeared on top. Now wrap the foil over the salmon to make a loose but tightly sealed parcel. Then place the foil parcel on a large baking sheet, diagonally so that it fits in the oven. If it seems a bit long bend the tail end upwards and then bake in the centre of the oven for 2½ hours.

After the 2½ hours, remove the salmon from the oven and allow it to cool completely before serving. (It's best not to open the foil.) To serve, the skin will come off very easily if you first make a horizontal slit all along the middle of the salmon. Then just ease the fillets away from the bone. Serve with the sauce, some crisp dressed salad leaves, such as Cos lettuce, and cucumber, and hot buttered new potatoes or potato salad.Note: this recipe contains raw eggs